You probably don’t need an Apple II to speak of. But that’s no reason not to do something if the mood strikes you, which is surely the mentality behind this particular project.
It’s a particularly impressive little bit of hackery, considering that, as Make points out, it’s running a self-built Apple II emulator on an Arduino Uno, living within the confines of 2KB of RAM, half that of the original Apple II. Somehow, there’s still 1.5KB of useable RAM to actually play with.
And now I feel the urge to play some Conan.